1. Field of the Invention
The present invention relates to a sitting device used for sitting on flat surfaces and that device is able to prevent spinal diseases, such as cervical, thoracic, and lumbar diseases, to occur.
2. Description of the Relevant Art
Wrong sitting postures lead to many spinal diseases. Sitting in a correct posture (see FIG. 8A) means keeping the pelvis in its neutral position, like in the same position when a person is standing, i.e. both right and left pelvis are upright, symmetrically arranged in two sides of the sacrum in a position higher than that of the two seating areas and located at the center. When the pelvis is in a neutral position, they allow the spine to not tilt to the right or the left and remain in its natural curve as the S-letter, meaning the whole body weight is distributed and balanced evenly over the vertebrates and discs of the spine. As a result, spinal diseases are less likely to happen. However, when sitting on flat surfaces, such as a floor, it is very hard to always sit in a posture that keeps the pelvis in such a neutral position, because the feet and two buttocks are in the same plane, the sacrum will be lowered due to the pelvis's sliding forward, the spine shall be bent, changing its posture from the S-letter to the C-letter, the vertebrae shall be pressed in the front parts and opened in the rear, causing back pain due to excessive pressure, pinching the disc, leading to its protrusion backwards to press on the nerves or the spinal cord and the pelvis, sacrum, coccyx is deflected and distorted, losing their balances that result in a change of the pelvic shape such as distortion, humpback and loss of curvature. Over time, sitting in wrong postures leads to many spinal diseases such as cervical, thoracic, and lumbar diseases. As a result, the person experiences back, neck and joint pain, tension-headaches, fatigue and stress related conditions, and many other health problems such as disc herniation, spondylolisthesis. Examples of wrong sitting postures have been shown in FIGS. 8B and 8C, wherein FIG. 8B illustrates the severe exhaustion sitting posture and FIG. 8C shows the degenerative exhaustion sitting posture.
In fact, many people have to sit on flat surfaces, such as on the floor, for the long time due to different reasons, for example, to do their work, to meditate, or to attend religious sessions. Without any supporting device to keep the pelvis in a straight posture while sitting underground, they soon experience back pain and commonly encounter one or some of the spinal diseases mentioned above.
Many devices have been invented to provide support when sitting on flat surfaces. However, they do not provide stable support that keeps the pelvis always in its neutral position, i.e., the key to sitting in a correct posture. Zafus is one of those. Stuffed with fluffy, soft, downy materials, a zafu or seat cushion raises the hips and partially absorbs the reaction force generated by the floor under the gravity force of the body of a sitter, making sitting in a leg-folding posture or the crossed-legged posture, a.k.a. Lotus sitting posture, more comfortable. However, due to the use of the fluffy materials, a zafu does not provide a stable support; the sitter's pelvis, coccyx can tilt in various directions depending on the sitting posture, eventually causing back pain and other spinal problems.
U.S. Pat. No. 6,141,807 discloses an adjustable height pillow that can “encourage proper sitting positions.” However, the pillow is stuffed with a soft flexible material in order to primarily form a shape to hold the whole croup, therefore cannot provide a stable support to keep the pelvis always in its neutral position.
U.S. Pat. No. 5,652,983 presents a sit/sleep constructed pillow that can provide comfort when sitting on it. However, it also does not provide stable support that can keep the pelvis in its neutral position.